Module 2-3: Newton's Third Law

Module 2-3: Newton's Third Law

Honors Physics

Multiple Choice

The tendency of an object to resist changes in its motion is...

• inertia
• force
• acceleration
• velocity

Multiple Choice

The fundamental unit of force is

• m/s
• m/s²

• N

• kg

Multiple Choice

According to Newton's Second Law, if you increase the force applied to an object:

• It accelerates more
• It doesn't move
• You get more inertia
• It decelerates

Multiple Choice

A cannonball with a mass of 0.5 kg is flying at an acceleration of 10 m/sec/sec. What is it's force?

• 50 Newtons
• 5 Newtons
• 20 Newtons
• 9.5 Newtons

​Newton's Third Law

• ​Any action creates an equal and opposite force.

• ​​Involves two objects each with an equal and opposite force.

  • When you push a wall, the wall pushes you with equal force but in the opposite direction.

  • ​When Earth's force of gravity pulls down on you, you pull back with equal force but in the opposite direction.

Third Law in Action

When a car on the highway hits a bug, who experiences more force?​

​

• ​Compare their masses

• ​Observe their accelerations

​Recall from Newton's Second Law

​Action-Reaction Pairs

​Forces always occur in pairs and are:

• ​the same type of force

• equal in strength

  opposite in direction

​Two More Examples

Poll

When two objects interact, they apply forces to each other of equal magnitude and opposite direction. In other words, every action has an equal and opposite reaction.

• I don't get it.

• I GOT IT!

Multiple Choice

When a swimmer is swimming, their arms push BACKWARDS against the water. In turn, the water pushes __________ against their arms allowing the swimmer to swim.

• DOWN

• UP

• FORWARD

• BACKWARD

Multiple Choice

When a bird is flying, their wings are pushing DOWN against the air. In turn, the air pushes __________ against their wings allowing them to fly.

• DOWN

• UP

• FORWARD

• BACKWARD

Multiple Choice

She throws the ball FORWARD against the wall and the wall pushes the ball _______________ toward her face with equal force! Ouch!

• UPWARD

• DOWNWARD

• FORWARD

• BACKWARD

Multiple Choice

When a heavy football player and a light one run into each other, who exerts more force? (pushes harder)

• The light one

• They exert the same force on each other

• The heavy one

Multiple Choice

Kids pull on a wagon. As they pull there is a force acting

• upon the wagon but not on the kid

• upon the kid but not on the wagon

• upon the kid and the wagon

Multiple Choice

A person is attracted towards the center of Earth by a 440N gravitational force. The force with which Earth is attracted toward the person is

• More than 440N

• Less than 440N.

• 440N.

Multiple Choice

When you jump up, you push the earth downwards. Why can't you tell that the earth has moved?

• The force of you jumping up doesn't actually push the earth down.

• The earth has much more mass so it doesn't move at all

• The earth is firmly rooted

• The earth has much more mass so you can't tell that it moved

Poll

After this lesson, how do you feel about Newton's Third Law?

• I feel very confident!

• I am somewhat confident.

• I am pretty confused.

• I am totally lost!